As electric vehicles such as electric automobiles use electric motors as power sources for driving by receiving electric power supplied from batteries, the batteries must be charged when the charged amount is depleted.
Generally, a battery for an electric vehicle needs to be charged after several tens of hours of traveling. Further, a battery naturally discharges electricity even if it is not used. As such, when an electric vehicle has not been used for a long time, as the battery capacity is reduced although it was fully charged, the battery may be required to be charged even if the vehicle has not been traveling.
Patent Document 1 discloses an art to calculate expected electric power usage according to schedules such as a distance and time to be used, and compare the expected electric power usage with the residual of the current charged amount of the battery to thereby determine whether or not charging is required.
Patent Document 2 discloses an art to automatically charge a battery when the residual capacity of the battery is reduced after an ignition switch was turned off.
Patent Documents 3 and 4 disclose an art enabling transmission of electric power between an electric automobile and a home. More specifically, Patent Documents 3 and 4 disclose an art to learn power consumption according to a traveling history, calculate an amount of secured electric power which is required to be secured for a battery, and supply electric power from the battery to the home side while limiting to a range in which the amount of secured electric power and the amount of electric power for emergency use are subtracted from the residual amount of the battery.
PATENT DOCUMENT 1: JP 2002-315193 A
PATENT DOCUMENT 2: JP 8-126120 A
PATENT DOCUMENT 3: JP 2001-8380 A
PATENT DOCUMENT 4: JP 2001-258177 A